1. Field of the Invention
The present invention relates to a flexible hose as described in the preamble of the first claim. This invention further relates to a profile for the production of this hose and a method for the production of this hose.
2. Background
A flexible hose with a corrugated inner and outer wall is for example used in vacuum cleaning systems and drainage systems.
In vacuum cleaning systems in which air, possibly in combination with dust particles, is transported through the hose, a part of the air and/or the dust particles will collapse with the multitude of internal grooves, present on the inner surface of the wall of the hose beneath the multitude of external protrusions of the outer surface. This increases the flow resistance for the air and/or dust particles, which results in a decrease of the maximum potential that is available at the suction mouth for sucking up the dust. Moreover, the presence of the internal grooves can, for a specific shape and number, also lead to a whistling of the hose. In drainage systems, the corrugated inner surface has the disadvantage that dirt can accumulate between the grooves, which can cause undesirable clogging and odor formation.
EP-A-1969987 describes a flexible vacuum cleaning hose in which the occurring whistling of the hose is reduced. Thereto a shielding is provided on the inner surface of the wall for closing each of the internal grooves. This shielding is for example formed by a first closing leg of a first profile and a second closing leg of an adjacent profile, the second closing leg being directed to the first closing leg. The first and second closing legs are bent towards the inside of the hose and overlap at least partially with each other. Hereby, the access of air and/or dust particles to the internal grooves is blocked and the undesirable whistling is reduced. However, because the first and second leg overlap at least partially with each other, an uneven surface is formed, as a result of which the flowing resistance for the air and/or dust particles, inside of the hose is increased and the dust can accumulate in the hose. This is undesirable.
JP-A-11159668 describes a flexible hose comprising a corrugated wall that comprises a multitude of internal and external grooves and protrusions. The flexible hose is formed by spirally winding of an S-shaped profile. In a specific embodiment of the flexible hose, each of the internal grooves is formed by a first S-shaped profile part closed by a closing leg of an adjacent second S-shaped profile part for the formation of a smooth inner surface. The closing leg extends from an upright leg of the first S-shaped profile part over the entire length of the internal groove up to and underneath the laying leg of the internal protrusion. The length of the closing leg is in other words substantially equal to the length of the S-shaped profile part. The closing leg thereby substantially increases the weight of the hose. Moreover, while bending the hose in an inward direction, the increased length of the closing leg will result in a reduction of the inner diameter of the hose, an uneven inner surface of the outer curve of the hose and an increase in the air resistance throughout the hose.
The corrugated outer surface of a flexible hose can also lead to an undesirable accumulation of dirt between the consecutive external grooves. The corrugated outer surface also has the disadvantage that the hose easily gets stuck behind objects which creates difficulties in using the hose. This is especially so in the case of vacuum cleaning hoses in central vacuum systems. Therefore, to make the outer surface more smooth, often some sort of stocking is pulled over the hose, which has a disadvantageous effect on the weight and the cost-price of the hose.